Thirdhand smoke poses lingering danger

Harmful cigarette chemicals can pollute indoor air for hours

Toxic compounds in smoke can linger on surfaces and in the air, producing gases and particles that can be inhaled long after a cigarette has been put out.


The stale smell of cigarettes is causing fresh worries. Even long after the smoke clears, every cigarette leaves behind airborne pollutants that are seriously harmful, experts now conclude.

Those lingering pollutants are called thirdhand smoke. And they may cause up to 60 percent of smoke’s harm to nonsmokers, scientists report. Their findings suggest that even smokers who light up only when they are alone may harm others who later come into a room that still smells of smoke. That harm can include cutting short a person’s lifespan by a full year or so.

Firsthand smoke is what a cigarette smoker inhales. Anyone nearby who breathes in pollutants from the air is being exposed to what’s called secondhand smoke. Thirdhand smoke is what still persists in the air many hours later. This pollution can last even hours after any visible smoke has disappeared. That stale, smoky smell comes from inhalable particles and fumes that were spewed earlier, when a cigarette burned.

Dangerously high levels of some wafting pollutants can haunt indoor airfor up to 18 hours, researchers now report. They based their results on laboratory tests and air samples from a smoker’s home.

“This is enormously important,” says pediatrician Jonathan Winickoff. He works at Massachusetts General Hospital in Boston. The new study “reinforces the notion that it’s not safe to smoke in any indoor or closed environment,” he says.

Researchers have known for a long time that chemicals from smoke can settle onto surfaces indoors. These chemicals can themselves be hazardous. They also can react with common indoor chemicals to form carcinogens. These cancer-causing substances pose a risk to young children in particular. That is because toddlers can put into their mouths toys and other objects coated with these pollutants. Still, little was known about what might be inhaled from thirdhand smoke.

Hugo Destaillats works at Lawrence Berkeley National Laboratory in California. To find out what’s in thirdhand smoke, he and his colleagues monitored air inside a room-sized chamber. Earlier, six cigarettes had been smoked in that chamber. Over the next 18 hours, the researchers measured levels of 58 different chemicals. They also measured tiny airborne particles that can lodge deeply in the lungs.

Levels of most particles and gases fell within 20 minutes, the study showed. However, some chemicals lingered. A few new chemicals showed up. And several compounds spiked to dangerously high concentrations. For instance, levels of a poisonous organic compound — acetonitrile (AH-see-toe-NIGH-trill) — rose after two hours. So did levels of the irritant 2-butanone (BU-tah-NOAN). Both compounds remained in the air for the full 18 hours.

Three chemicals in thirdhand smoke hit levels considered harmful by some state environmental agencies, the new study found. These included acrolein (Aa-CRO-LEE-un) and methacrolein. Both irritate the eyes and lungs. The third chemical was acrylonitrile (AA-krill-oh-NIGH-tril). It’s a highly flammable, toxic compound that some studies have linked to cancer.

The researchers also sampled the air in a smoker’s home. Similar chemical signatures of thirdhand smoke showed up there. That backed up the new laboratory findings. The researchers shared their findings online October 15 in Environmental Science & Technology.

“These compounds are quite reactive and they’re quite dangerous,” says chemist Lara Gundel, a researcher at the Berkeley lab. “And they’re not mentioned very often in secondhand smoke.”

Over 50 years, a nonsmoker living with someone who smokes 28 cigarettes a day would probably lose about a year of life — and perhaps as many as seven years, the researchers estimate. The premature death would be due to the long-term inhalation of both secondhand and thirdhand smoke. Most of the harm would come from inhaling the tiny particles produced when tobacco is burned, the research suggests.

Power words

acetonitrile     Also known as methyl cyanide, this compound is a colorless liquid that dissolves in both water and alcohol. It’s used as a solvent, to help other materials dissolved into such materials. The chemical is highly reactive and fairly toxic.

acrolein   A liquid that’s clear or yellowy and has an odor that can create a choking sensation. In high concentrations it’s a known poison. Manufacturers add it to plastics, medicines, pesticides, resins and more.

acrylonitrile     Also known as vinyl cyanide, this chemical is a known cancer-causing agent. It can be inhaled or absorbed through the skin. It is colorless, flammable, explosive and has a mild odor. It is best known as a chemical used in making acrylic fibers and other polymers (including synthetic rubber) and as a chemical to kill pests that infest stored grains.

2-butanone   Also known as methyl-ethyl-ketone, this colorless solvent has a smell similar to nail polish remover (acetone). It is flammable and explosive. It can have narcotic properties in people who inhale too much of it, meaning it will dull their senses and make them sleepy.

carcinogen  A substance, compound or other agent (such as radiation) that causes cancer.

flammable  Something that can burn (go up in flames) easily.

organic  (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms.

pollutant  A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

reactive   (in chemistry)  The tendency of a substance to take part in a chemical reaction that leads to new chemicals or changes in existing chemicals.

secondhand smoke  The gas and smoke particles emitted out of the burning end of a cigarette and exhaled by smokers. This pollution can be toxic and hand into the air (where it is available to be breathed in) for hours. Government scientists report that this secondhand smoke may contain up to 7,000 different chemicals, including hundreds that may be toxic (70 of which can cause cancer). According to the U.S. Centers for Disease Control and Prevention, since 1964, some 2.5 million nonsmokers have died from exposure to secondhand smoke.

thirdhand smoke    A mix of air pollutants that linger in air long after a cigarette has been smoked. Some can be quite toxic remain available to breathe in 18 hours or more after a cigarette has been smoked.

tobacco  A plant cultivated for its leaves. Dried tobacco leaves are burned in cigars, cigarettes, and pipes. Tobacco leaves are also sometimes chewed. The main constituent of tobacco leaves is nicotine.

toddlers    Children between 9-months and 2-years old. The term refers to the fact that these youngsters only recently learned to walk and are not yet totally steady on their feet.

toxic  Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

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